1. Field of the Invention
The present invention relates to a contact structure. More particularly, the present invention relates to a contact structure used for the electrical connection of electronic parts represented by LSI, in other words, a contactor. Especially, the present invention relates to an anisotropic conductive sheet used as a contactor in the electrical connection between circuit devices such as electronic parts or used as a contactor in the inspection apparatus used for inspecting the operation of circuit devices such as a printed circuit board and semiconductor integrated circuit. The present invention also relates to an electronic device and inspection apparatus for operation test into which the above conductive sheet is incorporated. Note in this specification that the term “LSI” is frequently used, and as long as a specific notice is not given, the term “LSI” means, of course, various electronic parts represented by LSI and VLSI, and further means other parts and elements useful in the practice of the present invention.
2. Description of the Related Art
Recently, the technology of producing semiconductor substrate and others has been remarkably developed, and according to the development of the production technology, the pattern of LSI wiring has been made remarkably fine and, further, the number of LSI terminals has been remarkably increased and, furthermore, the terminals have been made remarkably fine. Concerning the form of using LSI, there is a strong demand of downsizing and packaging the parts at high density. This will be easily understood from the fact that portable apparatuses, the size of which must be small and the performance of which must be high, for example, cellular phones, PHS phones, mobile personal computers, cameras integrated with a videorecorder and electronic computers of high performance, in which a distance between LSIs adjacent to each other is minimized so as to ensure operation at high speed, are widely spread and put on the market.
The form of delivery of LSI is changing according to the recent tendency described above. That is, attention is paid to the method of delivery of LSIs in which LSIs are delivered not being packaged, that is, LSIs are delivered in the form of LSI chips, and further, LSIs are delivered after the performance of LSIs have been guaranteed so that the performance of LSIs, which are not packaged, is the same as that of packaged LSIs. Actually, there is an increasing demand of the delivery of LSIs in which LSIs are delivered as KGD (Known Good Die) or LSIs are delivered as CSP (Chip Size Package) which is a small package, the size of which is the same as that of the LSI chip.
Due to the above circumstances, it is indispensable to provide a contact structure (contactor) capable of positively coming into contact with fine terminals of multiple pin structure which are arranged in LSI so that the operation and quality of an LSI can be tested.
Further, from the viewpoint of enhancing the efficiency of an LSI test, there is a strong demand of the test (FT: Final Test or BI: Burn In) in which LSI is not separated into individual chips but LSI is kept in the form of a wafer and all LSIs are simultaneously tested all at once. When all LSIs are simultaneously tested all at once, for example, the following effects can be expected.
1. Handling efficiency can be enhanced.
When chip sizes are different from each other, the handling device cannot be used for general purpose. However, when wafers are handled, all wafers can be simultaneously conveyed all at once because the sizes of the wafers are standardized.
2. Information of defective product can be managed by a wafer map.
In addition to that, according to wafer level CSP, which has been recently developed and disclosed, all processes from the wafer process to the final assembling process (packaging process) can be executed in the form of the wafer. If it becomes possible to conduct testing in the form of the wafer, the efficiency of the process can be more enhanced.
However, as described above, the terminals of each LSI has become fine and the number of the terminals of each LSI has been increased. Therefore, it is very difficult to realize a contactor capable of simultaneously coming into contact with a plurality of terminals of LSI which is kept in the state of a wafer and, if possible, a contactor capable of simultaneously coming into contact with all terminals of LSI on a wafer all at once. Realization of such a contactor has become a common problem to be solved in the industry.
As a contactor capable of solving the above problems, for example, there have already been proposed a needle type mechanical probe and a membrane type probe. However, the above probes are disadvantageous as follows. The costs of both the needle type mechanical probe and membrane type probe are high. Further, in the former needle type mechanical probe, as the individual pins are obliquely arranged, the arrangement and positional accuracy of needle ends are limited. In the latter membrane type probe, the contact electrodes cannot be freely moved.
Thus, in order to solve the above problems, an anisotropic conductive rubber sheet was devised. As a base material of this anisotropic conductive rubber sheet, rubber is used, and electric conductive material such as metallic particles or metallic wires is incorporated into the rubber only in the thickness direction. For example, Japanese Unexamined Patent Publication (Kokai) No. 51-93393 discloses a method of producing an elastic contact sheet (a dispersion type anisotropic conductive elastomer sheet) characterized in that conductive metallic particles are aligned in one direction and dispersed in an flexible insulating material (elastomer). Further, Japanese Unexamined Patent Publication (Kokai) No. 53-147772 discloses a method of producing a conductive elastomer (an uneven-distribution type anisotropic conductive elastomer sheet) capable of exhibiting conductivity upon pressurization including a large number of conductive passage forming sections extending in the thickness direction and also including an insulating section to insulate the large number of conductive passage forming sections from each other when conductive magnetic particles are unevenly distributed in a high polymer elastic body. Furthermore, Japanese Unexamined Patent Publication (Kokai) No. 61-250906 discloses an example in which the uneven-distribution type anisotropic conductive elastomer sheet is improved. This improved example is characterized in that a step portion is formed between the surface of the electric conductive passage forming section and that of the insulating section.
According to the latest examples, Japanese Unexamined Patent Publication (Kokai) No. 2000-11766 discloses an anisotropic conductive sheet which is schematically shown in FIG. 1. The anisotropic conductive sheet shown in FIG. 1 is characterized in that the electrical continuity section 52 containing conductive particles 53 in the insulating material is formed and that the insulating portion 55 except for the electrical continuity section 52 is made of an elastic insulating body and that the insulating portion 55 contains insulating particles 54.
However, these and other anisotropic conductive elastomer sheets of the prior art still leave room for improvements. For example, the above anisotropic conductive elastomer sheets of the prior art have the following problems.
(a) The life span is short.
Especially when the anisotropic conductive elastomer sheets are used at high temperatures, the rubber section is plastically deformed. Therefore, the above anisotropic conductive elastomer sheets of the prior art can be used only once or several tens of times. For example, in the case of a BI Test, high temperatures not lower than 125° C. are applied. Therefore, the above problems become remarkable.
(b) It is impossible to cope with a small pitch.
It is difficult to incorporate conductive material into the anisotropic conductive sheet. Therefore, the pitch between the electrical continuity sections is usually about 500 μm. The pitch between the electrical continuity sections is about 200 to 150 μm at the most preferred instances.
(c) It is impossible to accomplish a predetermined electrical connection.
In general, a surface electrode of the semiconductor integrated circuit is made of aluminum, the mechanical strength of which is low. Therefore, in order to enhance the mechanical strength of the surface electrode, an oxide film of aluminum is formed on the surface. As the mechanical strength of this oxide film of aluminum is high, when the sheet is connected with an electrode, it is difficult for the electrical conductive passage section of the sheet to pierce the oxide film of aluminum. As a result, it is impossible to attain a predetermined electrical connection. Especially when the sheet is connected with the electrodes all at once, although the sheet can be partially connected with the electrodes, it is impossible to connect the sheet with all the electrodes uniformly and stably.
(d) Circuit apparatus and others are polluted.
In general, silicone rubber is used as the elastic high polymer material composing the anisotropic conductive elastomer sheet. However, since this silicone rubber contains silicone oil of low molecular weight, for example, when the elastomer sheet is used for the inspection of a circuit device over a long period of time, silicone oil bleeds out onto the sheet surface. By this silicone oil bleeding out onto the sheet surface, a surface of the electrode to be inspected, which is an object of inspection, is polluted. As a result, when the circuit device is mounted, it becomes impossible to conduct bonding and further it becomes impossible to attain a predetermined electrical connection.
Some trials have been made to solve the above problems. For example, as shown in FIG. 2, Japanese Unexamined Patent Publication (Kokai) No. 2000-235877 discloses an uneven-distribution type anisotropic conductive sheet 60 having a base material of the sheet in which a plurality of elastic conductive passage forming sections 62 respectively extending in the thickness direction are arranged being insulated from each other by the insulating section 64. This anisotropic conductive sheet 60 is characterized as follows. On the anisotropic conductive sheet 60, on the electrical conductive passage forming section 62 which has been formed by the orientation treatment of electric conductive fine particles, the conductive material 66 used for the contact made of a metallic sheet or metallic film is integrally arranged via the conductive adhesion layer 65 in which conductive powder is dispersed in hardening resin. However, the following problems may be encountered in the case of the above anisotropic conductive sheet 60. The conductive material 66 used for the contact is made of hard material such as a metallic sheet or metallic film. Further, the base material of the conductive material 66 used for the contact is hard and not elastic. Therefore, it is impossible to successfully pierce an aluminum oxide film of which is a protective film for protecting the electrode surface. Further, the production process is complicated in such a manner that hardening treatment must be conducted under the condition of a parallel magnetic field, which causes an increase in the production cost.